1,721,178 research outputs found
Dynamic alterations in T-lymphocyte subsets assessed by flow cytometry in chickens following exposure to infectious bursal disease virus: A systematic review
Full text linkInfectious bursal disease virus (IBDV) is a significant pathogen in poultry, causing acute immunosuppressive disease in young chickens. While B-lymphocyte involvement in IBDV pathogenesis is known, the role of T-cells is incompletely understood. This systematic review presents the alterations in chicken T-lymphocyte subsets after IBDV exposure, assessed by flow cytometry analysis. Four databases were queried for identifying eligible studies focused on experimental infections measuring T-lymphocyte changes in the bursa of Fabricius, spleen, thymus, and peripheral blood mononuclear cells. Of 488 studies found, 25 met the pre-established criteria and were included in the qualitative synthesis of results. Most studies analysed T-lymphocyte responses during the acute phase of IBDV infection, primarily focusing on CD4+ and CD8+ T-cells. Other subsets, such as γδ T-cells and double-positive CD4+CD8+ T-cells, were less frequently investigated. An increase in T-lymphocytes was noted in the bursa of Fabricius, suggesting their active role in viral clearance. In the spleen, CD4+ T-cells commonly increased, while CD8+ responses varied among studies. Increased levels in T-cells were also noted during the chronic infection in the bursa of Fabricius, possibly due to persistent viral antigens. Overall, variations in flow cytometry methods and T-cell output reporting were noted among studies. Based on the data collected, further investigation into diverse T-cell subpopulations beyond CD4+ and CD8+ is needed, as well as the standardization of flow cytometry assays in chickens
Two similar commercial live attenuated AMPV vaccines prepared by random passage of the identical field isolate, have unrelated sequences
No full textSince late ‘80 s Avian metapneumovirus subtype A causes sufficient disease in Europe for commercial companies to have started developing live attenuated vaccines. Here, two of those vaccines were fully consensus sequenced alongside their progenitor field strain (#8544). Sequences comparison shows that the attenuation of field strain #8544 was associated with no common substitutions between the two derived vaccines. This finding suggests that the attenuation of field viruses via serial passage on cell cultures or tissues is the result of a random process, rather than a mechanism aiming to achieve a specific sequence. Furthermore, field vaccination strategies would greatly benefit by the unambiguous vaccine markers identified in this study, enabling a prompt and confident vaccines detection
Salmonella enterica Serovar Infantis in Broiler Chickens: A Systematic Review and Meta-Analysis
Full text linkSalmonella enterica subsp. enterica serovar Infantis poses a growing threat to public health, due to its increasing prevalence worldwide and its association with high levels of antimicrobial resistance. Among livestock, S. Infantis is especially isolated from broilers. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review was conducted by searching in three databases (Web of Science, Scopus, and PubMed) for English-language studies (1957–2023) that reported the prevalence of S. Infantis in broiler farms. Eligible studies included epidemiological investigations conducted in broiler chickens by sampling the house environment (flock-level prevalence) or the birds (individual-level prevalence). A random-effect model was applied to calculate S. Infantis pooled prevalence estimates with 95% confidence intervals (CIs). Furthermore, to assess between-study heterogeneity, the inconsistency index statistic (I2) was calculated. Among 537 studies retrieved, a total of 9 studies reporting flock-level prevalence of S. Infantis and 4 reporting individual-level prevalence were retained for analysis. The flock-level pooled prevalence was estimated to be 9% (95% CI: 1–26%) and a high between-study heterogeneity was found (I2 = 99%, p < 0.01). Concerning individual-level prevalence, a meta-analysis was not performed due to the scarcity of eligible studies. The data presented underscore the significant occurrence of S. Infantis in broilers at the farm level. By summarizing the existing literature, this work provides useful insights for conducting future surveys of Salmonella spp. in live broiler chickens as a preliminary step for developing more efficient control strategies
Rapid, Sensitive, and Species-Specific Detection of Conventional and Recombinant Herpesvirus of Turkeys Vaccines Using Loop-Mediated Isothermal Amplification Coupled With a Lateral Flow Device Readout
Full text linkMarek's disease, an economically important disease of chickens caused by virulent serotype 1 strains of the Mardivirus Marek's disease virus (MDV-1), is effectively controlled in the field by live attenuated vaccine viruses including herpesvirus of turkeys (HVT)—both conventional HVT (strain FC126) and, in recent years, recombinant HVT viruses carrying foreign genes from other avian viruses to protect against both Marek's disease and other avian viral diseases. Testing to monitor and confirm successful vaccination is important, but any such test must differentiate HVT from MDV-1 and MDV-2, as vaccination does not prevent infection with these serotypes. End-point and real-time PCR tests are widely used to detect and differentiate HVT, MDV-1 and MDV-2 but require expensive specialist laboratory equipment and trained operators. Here, we developed and validated two tube-based loop-mediated isothermal amplification tests coupled with detection by lateral flow device readout (LAMP-LFD): an HVT-specific test to detect both conventional and recombinant HVT strains, and a second test using novel LAMP primers to specifically detect the Vaxxitek® recombinant HVT. Specificity was confirmed using DNA extracted from virus-infected cultured cells, and limit of detection was determined using plasmid DNA carrying either the HVT or Vaxxitek® genome. The LAMP-LFD tests accurately detected all HVT vaccines, or Vaxxitek® only, in crude DNA as well as purified DNA extracted from field samples of organs, feathers, or poultry house dust that were confirmed positive for HVT by real-time PCR. These LAMP-LFD tests have potential for specific, rapid, simple, and inexpensive detection of HVT vaccines in the field
Avian Metapneumovirus
No full textAvian metapneumovirus is the type species of the genus Metapneumovirus in the subfamily Pneumovirinae within the Paramyxoviridae family. The genome encodes eight discrete transcription units, which are generally assumed to code for nine proteins. Genes are anked by a 3′ leader and 5′ trailer in the order 3′–N (nucleocapsid)–P (phosphoprotein)–M (matrix)–F (fusion)–M2 (second matrix)–SH (small hydrophobic)–G (glycoprotein)–L (large polymerase)–5′. Virions are pleomorphic, with sizes ranging from 50 nm to more than 200 nm. Based on the level of genetic variation and antigenic difference, aMPV isolates have been classi ed into four distinct subtypes: A, B, C and D. Turkeys and chickens are the most susceptible species and show an upper respiratory disease and reproductive disorders when infected. Pheasants, guinea fowls and ducks can also be affected and develop clinical disease. After its rst appearance in South Africa in the late 1970s, aMPV has been reported worldwide. The main approach to control of aMPV is by the use of live attenuated and inactivated vaccines. Several research groups have attempted development of a novel generation of vaccines, but for each of these approaches protection has been inferior to that afforded by live vaccines
Longitudinal field studies of Avian metapneumovirus and Turkey hemorrhagic enteritis virus in turkeys suffering from colibacillosis associated mortality
No full textThe aim of this study was to evaluate if the exposure to Avian metapneumovirus (aMPV) and/or to Turkey hemorrhagic enteritis virus (THEV) was significant for the induction of episodes of colibacillosis in aMPV and THEV vaccinated turkeys. Colibacillosis-associated mortality was recorded and longitudinal virological studies performed in three consecutive turkey flocks reared in the same farm. aMPV and THEV diagnostic swabs and blood samples were made once a week up to 14 weeks of age. Swabs were processed by molecular techniques for viruses detection and antibody titres were evaluated. Field subtype B aMPVs were detected in all flocks at different ages of life always associated with respiratory signs and increase of colibacillosis-associated mortality. THEV has been consistently detected in all flocks since the 9th week of age. Vaccination with a single dose of the THEV commercial inactivated vaccine available in Italy seems does not protect the birds from the infection. Sequence comparison of the hexon protein of one of the THEV strains detected, and strains isolated worldwide, revealed high similarity between them. These results are consistent with the notion that the hexon protein, being the major antigenic component of the virus, is highly conserved between the strains. Results showed that field aMPV infection is directly correlated to colibacillosis-associated mortality. Less clear appears the role of THEV because the endemicity of aMPV makes difficult to evaluate its role in predisposing colibacillosis in absence of aMPV. It would be interesting to further investigate this issue through experimental trials in secure isolation conditions
Molecular characterization of whole genome sequence of infectious bronchitis virus 624I genotype confirms the close relationship with Q1 genotype
Full text linkInfectious Bronchitis virus (IBV) genotype Q1 was detected for the first time in China in 1996, and then spread worldwide. The first report of Q1 genotype in Italy occurred in 2011 and a deep molecular investigation of a Q1 isolated in Italy in 2013 has led to speculation regarding the origin of this genotype. Phylogenetic analysis of the S1 sequence of a Q1 Italian strain revealed a close relationship with sequences of the 624I strains circulating in Italy in the early 1990s and this led to the idea that 624I was an ancestor of the Q1 genotype. Despite the fact that most heterogeneity of IBVs occurs in the S1 gene, the sequence analysis of this gene alone was not sufficient to confirm or deny this hypothesis. In the present study, an Italian 624I (gammaCoV/AvCov/Ck/Italy/IP14425/96) was fully sequenced for the first time and compared to all available complete Q1 genome sequences. This analysis confirmed the genetic correlation between GammaCoV/AvCov/Ck/Italy/IP14425/96 and Q1 strains, suggesting a common origin between 624I and Q1 genotypes
Effect of changes of vaccination strategies on IBV epidemiology, diagnosis and control: an Italian retrospective study
Full text link: Infectious bronchitis virus (IBV) is among the most impactful poultry pathogens, whose control, based on biosecurity and routine vaccination, is hampered by the existence of countless genetic variants sharing poor cross‐protection. A retrospective study was conducted on IBV positive samples collected in Italian broiler farms from 2012 to 2019. In 2015, the adopted vaccination protocol shifted from a Mass and 793B‐based vaccines to the administration of Mass and QX vaccines, allowing to study how changes in vaccination strategies may affect IBV epidemiology, control and diagnosis in the field. The most frequently detected lineages were QX (70.3%), 793B (15.8%) and Mass (11.9%). The relative frequencies of QX and 793B detections remained stable throughout the study, while Mass detections significantly increased after the vaccination change. Rather than to an actual growth of Mass population size, this finding may be attributable to different vaccine interactions, with Mass strains being more frequently concealed by 793B vaccines than by QX ones. Based on the obtained results, the two vaccination protocols appear to be similarly effective in fighting IB outbreaks, which in the last decade have been caused primarily by QX field strains in Italy. These results indicate that vaccination strategies may significantly affect IBV epidemiology and diagnosis, and should therefore be considered when choosing and interpreting diagnostic assays and planning control measures
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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